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ferlopezperez
Joined: 11 Feb 2003 Posts: 31 Location: Mexico City
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Posted: Tue Feb 24, 2004 5:02 pm Post subject: |
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Hi everybody, I've just started to draw my "frankenstein" camera, the idea of a mirror is wonderful to solve the focusing problem. The direct positive paper sounds great but it reminds me of my first attempt to build a camera (when I was 10 years old) it was a pinhole camera and used grade #3 kodak paper, the images were wonderful but they had to be reversed to obtain a positive image. If I put a ground glass on top, with a mirror in the middle, ¿how can I measure the distance to the film in relation with the ground glass? I guess it has to be the same distance, am I right? The camera I'm trying to build should be unique, the idea of 8x10 paper is something remarkable, but my lens is 150mm I think it won't cover the 8x10" image. Ideas like these ones are really valuable, most of all if you are new in the building-a-camera subject. Thank you all, if you have any other ideas I will appreciate them. |
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Nick
Joined: 16 Oct 2002 Posts: 494
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Posted: Tue Feb 24, 2004 5:50 pm Post subject: |
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I agree if building something unusual would be more interesting then just building something easily available off the shelf. There is one Ebay seller that sells older Ra-4 roll paper. I picked up two rolls and it seems just fine. 8" wide and 275' long. Something like an 8x16 or 8x20 or anything 8x would be possible. It could be cut down to 4x5 for testing or smaller prints.
I don't think a shutter is an issue. Paper is fairly slow. The way I understand it paper is in the ASA 6 range. You'll need an 85 filter [or is it an 80?] so that slows things down even more. You'll also be making an in camera orginal so diffraction shouldn't be an issue. Figure F/32 or F/45 or even smaller.
For B&W wouldn't paper negatives be possible? Avoiding any need for a complex setup to flip the image. |
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ferlopezperez
Joined: 11 Feb 2003 Posts: 31 Location: Mexico City
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Posted: Tue Feb 24, 2004 6:02 pm Post subject: |
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maybe the shutter is useful in order to use it in B only, just to control the opening and closing. The paper is available with my local film supplier, He has a stock of this and other old supplies. Do you think my 150mm schneider lens will cover an 8x10" area?
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t.r.sanford
Joined: 10 Nov 2003 Posts: 812 Location: East Coast (Long Island)
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Posted: Tue Feb 24, 2004 6:37 pm Post subject: |
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I'n pretty sure that a 150mm. "Xenar" will not cover 8X10 at infinity, though it surely will at 1:1.
Paper negatives certainly appeal; the trick is finding the right kind of paper. Kodak used to make a very lightweight base, "A" or "Ad Type" (good for prints that had to be cut accurately for pasting up on mechanical layouts), and art supply stores used to carry a "transparentizer" that could be used to make paper more translucent, as an aid to tracing drawings. If those products still exist and could be used in conjunction, something might be done.
Another possibility, of course, is to make the paper negative (as with the pinhole camera described) and then rephotograph it on paper stock at 1:1 to make what the photostat houses used to call a "second print." This would take care of the tonal reversal and the "flopped" image orientation.
It would, of course, do away with whatever advantage might be obtained from a contact print, but it also would prevent your having to deal with the paper fiber (though you might want that), and it wouldn't produce the typical "Callier effect" contrast enhancement experienced with condenser enlargers.
As for measuring from lens to film after introducing a mirror into the lightpath, a good deal would depend on accurate measurement before construction. Beyond that, you'd probably find it simplest to use a groundglass (or even a good enlarger focusing magnifier) to fix the final position of the sensitized-material support in the bottom of the body, then adjust the focusing screen on the top to conform. |
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RichS
Joined: 18 Oct 2001 Posts: 1468 Location: South of Rochester, NY
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Posted: Tue Feb 24, 2004 7:24 pm Post subject: |
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Just a side note about the actual construction. Some interesting ideas may be found in the book: Primitive Photography by Greene. He also has some ideas about home made lenses and such. Gotta get back to work
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